Spring’s the time to eliminate fire ants around the house

Tim Lockley/Special to the Sun Herald

This is a good time to treat your property for fire ants.

Fire ants build their mounds for specific purposes. They are very efficient creatures and will not waste energy building something unnecessary.

The No. 1 purpose of a mound is to get the colony up and away from saturated or flooded ground. These ants evolved in a flood plain in South America and have adapted well to periodic flooding.

The second reason for the mound is as a passive solar collector to keep the ants and the brood warm during the winter. When it’s cold, the ants will gather inside the mound on the sunlit side. This normally occurs on a sunny day about 10 a.m. This is where the advantage lies for us.

This time of year, before it gets too hot, we can readily find the mounds. In the hotter months, the raised mound may not even be constructed.

There are three proven elimination methods that are relatively easy and safe to use. The first is labor-intensive and limited in scope. It has one positive aspect the other two don’t have: instant gratification. Mix any liquid or other water-soluable insecticide in a bucket of water at the lowest rate on the label and pour a quantity sufficient to saturate the mound.

The average mound is slightly smaller than a basketball. Half a bucket should do the job. Depending on what chemical you use, the ants will be dead within 5 to 60 minutes. If you stand perfectly still and are very quiet, you can hear the ants scream as they suffer and die.

The second method is slower, but safe and very inexpensive. A number of baits are available. Amdro, the most common, contains a stomach poison called hydromethylon. Others might contain an insect growth regulator that sterilizes the queen. Baits work because of the way fire ants eat.

Worker ants consume almost nothing but liquids. The active ingredient in the various baits is suspended in soybean oil, then gets coated into a pregelled corn grit. The ants pick up the grit and remove the oil. Once the ant has been fed, it regurgitates the fluid and feeds it to the next ant down the line. Eventually, the poison is passed throughout and the colony dies.

During warmer months, most colonies will be eliminated within three weeks of the application. During colder periods or when the ants have more food access, it may take the active ingredient up to three months to work.

But there are two drawbacks to baits. First, the baits are designed to go out at a rate of 1.5 pounds per acre. Unless you have a spreader specifically designed to put out fire ant bait, it is very difficult to apply at that rate. With your typical small whirlybird-type spreader, you have to set the opening to as narrow a gap as you can, turn the handle slowly and walk really fast.

Some companies, recognizing this difficulty, have reformulated their bait so you have a larger amount to put out per acre. This makes it more practical but somewhat more costly.

The second drawback is the lack of residual effect. The bait will kill only the colonies that were there at the time of application. The bait itself is usually taken up by the ants within two to four hours after it hits the ground. Any missed granules will be quickly degraded by sunlight and moisture.

The third method is initially more expensive. This requires applications of granular insecticides. Any chemical labeled for use in your yard will work to some degree. Most last around three months. Ideally, you should use a combination of a bait or the granular treatment along with the drench treatment. This two-step approach will give you the best bang for the buck.

The use of the bait or the granular insecticides will eventually result in the demise of all the mounds within the treatment area — even the ones you don’t know about or can’t reach. Meanwhile, the drench method can be applied to those colonies that you have to get rid of quickly — the one next to the air conditioner or where pets or children are active. No matter your choice, make certain you read and follow the label directions carefully on any product you use.

Tim Lockley, a specialist in entomology, is retired from a 30-year career as a research scientist for the U.S. Department of Agriculture. For answers to individual questions, please send a stamped, self-addressed envelope to Tim Lockley, c/o Sun Herald, P.O. Box 4567, Biloxi MS 39535.